Shape memory polymer foams to seal space around valves

ABSTRACT

An embodiment includes individual SMP foams that radially expand and fill gaps around a heart valve that may be improperly seated, in an unusual cross section, or has poor apposition against a calcified lesion. Other embodiments are described herein.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.16/487,207, filed Aug. 20, 2019, which is a §371 national stage ofinternational application PCT/US2018/022498, filed Mar. 14, 2018, whichclaims priority to United States Provisional Patent Application No.62/471,131 filed on Mar. 14, 2017 and entitled “Shape Memory PolymerFoams to Seal Space Around Valves”. The content of each of the aboveapplications is hereby incorporated by reference.

TECHNICAL FIELD

Embodiments of the invention are in the field of medical devices and, inparticular, valves.

BACKGROUND

Surgery to replace a cardiac valve (e.g., aortic or mitral valve) isdone for various reasons, such as stenosis or regurgitation of themitral, aortic, pulmonary, or tricuspid valves. During this surgery, thedamaged valve is removed and replaced with an artificial valve. Thevalve replacement is typically an open-heart surgery. However, aminimally invasive surgery or a catheter procedure to replace the valvemay be an option for some people. The artificial valve might bemechanical (made of man-made substances) and/or may be made from animaltissue.

Paravalvular or paraprosthetic leak (PVL) is a complication associatedwith the implantation of a prosthetic heart valve whether by atraditional (surgical) or a transcatheter (TAVI) approach. Paravalvularor paraprosthetic leak refers to blood flowing through a channel betweenthe structure of the implanted valve and cardiac tissue as a result of alack of appropriate sealing. The majority of PVL are crescent, oval orroundish-shaped and their track can be parallel, perpendicular orserpiginous. Incidence of PVL, including small non-significant jets, isestimated to be as high as 20%. PVL is also more common with mitral (upto 20%) than aortic prosthetic valves.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the present invention willbecome apparent from the appended claims, the following detaileddescription of one or more example embodiments, and the correspondingfigures. Where considered appropriate, reference labels have beenrepeated among the figures to indicate corresponding or analogouselements.

FIG. 1 includes a shape memory polymer (SMP) foam substantially coveringa window of a stent in an embodiment.

FIG. 2A shows a radially compressed SMP foam in an embodiment. FIG. 2Bshows the SMP foam radially expanded.

FIG. 3A shows a radially compressed SMP foam in an embodiment. FIG. 3Bshows the radially compressed foam and a stent after the stent iscompressed for delivery into a patient.

FIG. 4 includes a radio-opaque monolithic SMP foam ring in anembodiment. This also demonstrates the machining capability for theembodiment (i.e., the ability to form the foam into various shapes andsizes).

FIG. 5A shows a low density foam matrix in an embodiment. FIG. 5B showsa high density foam that is doped for radio-opacity.

FIG. 6A shows an expanded SMP foam. FIGS. 6B and 6C show the SMP foamwhen crimped/compressed.

FIG. 7 shows various shapes and sizes that demonstrate the machiningcapability for embodiments.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like structures maybe provided with like suffix reference designations. In order to showthe structures of various embodiments more clearly, the drawingsincluded herein are diagrammatic representations. Thus, the actualappearance of the fabricated structures, for example in a photograph,may appear different while still incorporating the claimed structures ofthe illustrated embodiments. Moreover, the drawings may only show thestructures useful to understand the illustrated embodiments. Additionalstructures known in the art may not have been included to maintain theclarity of the drawings. “An embodiment”, “various embodiments” and thelike indicate embodiment(s) so described may include particularfeatures, structures, or characteristics, but not every embodimentnecessarily includes the particular features, structures, orcharacteristics. Some embodiments may have some, all, or none of thefeatures described for other embodiments. “First”, “second”, “third” andthe like describe a common object and indicate different instances oflike objects are being referred to. Such adjectives do not imply objectsso described must be in a given sequence, either temporally, spatially,in ranking, or in any other manner “Connected” may indicate elements arein direct physical or electrical contact with each other and “coupled”may indicate elements co-operate or interact with each other, but theymay or may not be in direct physical or electrical contact.

Many embodiments addressed herein concern paravalvular leaks. However,embodiments are more generally concerned with leaks associated withimplanted valves, whether those valves be cardiac valves, peripheralvenous valves, or otherwise.

Applicant determined conventional practices use, for example, PET(Dacron) “skirts” to fill the paravalvular space and promote tissueintegration. However, Applicant has further determined such technologiesfail to adequately do either of volumetrically filling the paravalvularspace or promoting tissue integration. Embodiments described hereinutilize shape memory polymer (SMP) foams to fill the space around thevalve and promote tissue integration.

For example, an embodiment includes use of a SMP foam incorporatedaround the annulus of a heart valve to reduce flow around the valve andhelp integrate the device into the surrounding tissue. Morespecifically, a SMP foam expands and fills gaps around a valve that maybe improperly seated, in an unusual cross section, or has poorapposition against a calcified lesion. For example, the radial expansionof the foam provides volumetric filling around the device. This appliesfor surgically placed valves, but the shape memory capacity of the foamis particularly useful for endovascular valve delivery.

While many embodiments herein address radial compression of SMP foams(and consequent radial expansion of the SMP foams), other embodimentsmay employ axial compression/expansion and/or circumferentialcompression/expansion.

Once implanted, the foam occludes paravalvular leaks and promotes tissueintegration for durable occlusion. The porous morphology of the foamencourages acute thrombus formation and device sealing. Over time, thisthrombus is replaced with integrated tissue for durable sealing anddevice incorporation into the surrounding tissue.

An embodiment includes a monolithic foam annulus adhered to a valve.See, for example, the foam annulus in FIG. 4. Adhesion includes weavingvalve support struts through the foam (see, e.g., FIG. 1), gluing valvesupport struts to the foam, and/or coating the valve support struts witha polymer (such as polyurethane) film and adhering the foam to thepolymer film. Adhering the foam to the valve support structure ensuresit will not dislodge and move downstream to occlude vessels.

As seen in FIG. 2B, an embodiment includes independent foam “scales”adhered to the device.

In an embodiment, Nitinol wire is threaded through polymer foam (seeFIGS. 1 and 3A). These wire structures would be threaded through thefoam prior to being welded together to form the support structure.

In an embodiment, a bottom of the SMP “scale” is not bound to theNitinol frame (see FIGS. 1, 3A, and 3B). The foam “scale” embodimentaccommodates the anisotropic strain (see, e.g., FIG. 3B) the valvesupport structure undergoes during radial compression into the deliverycatheter. For example, each window of the support structure decreasesalong the circumferential axis (see, e.g., “horizontal” arrows of FIG.3A that refer to movement of the Nitinol window), but elongates in theaxial direction (see, e.g., “vertical” arrows of Figure A that refer tomovement of the Nitinol window). In other words, the bottom of the scaleis free and prevents the foam from undergoing significant tension thatcould lead to tearing.

In an embodiment, the SMP “scale” includes a window (see upper void inSMP foam of FIG. 1) to accommodate welding or linking neighboringsupport struts.

Other scales are included in FIGS. 5A, 5B, 6A, 6B, 6C and 7. These foamform factors shown in slides 5A-7 demonstrate different degrees of areafilling within each “window” of the support structure. Different foamform factors allow for varying degrees of radial compression and scalefolding after compression. Once radially compressed, the flat foam scalemay be folded, similar to a catheter balloon, to achieve the minimalcrimped cross section that deploys appropriately during delivery.

While many embodiments above address valve sealing, and cardiac valvesealing in particular, other embodiments are not so limited and mayinclude, for example, abdominal aortic aneurysms (AAA) stent graftsealing and the like.

An embodiment includes a foam derived from a reaction between one ormore polyols (e.g., HPED and/or TEA) and one or more diisocyanates(e.g., hexamethylene diisocyanate (HDI), trimethyl hexamethylenediisocyanate (TMHDI), and/or isophorone diisocyanate) to form apolyurethane SMP. Embodiments include polyurethane SMP foams synthesizedby some combination of: HDI, TMHDI, isophorone diisocyanate,triethanolamine, diethanolamine, butane diol, butyne diol, N,N,N′,N′tetrakis (hydroxyl propylene) ethylenediamine

Other embodiments could include x-ray visible SMP foams. For example, anembodiment includes a foam derived from a reaction between one or morepolyols (e.g., 5-Amino-2,4,6-triiodoisophthalic acid;3-methyl-1,5-pentanediol; 2-butyl-2-ethyl-1,3-propanediol; Hexanetriol;Butanetriol) and one or more diisocyanates (e.g., HDI) to form apolyurethane SMP.

Embodiments provide various means to ensure the foam is protected duringdevice delivery.

In an embodiment the valve is delivered through a large diametercatheter/sheath which allows for a large delivery “ramrod” (that canaccommodate significant friction from the expanding device) to deploythe valve from the catheter/sheath. Due to the foam being adhered to thesupport structure (e.g., foam may be adhered focally to the struts oracross the full area of the window) the foam does not shear off duringdelivery.

With some transcatheter embodiments the foam has a delayed foamexpansion. For example, the device may be stored well below body tempand may be programmed (glass transition temperature (Tg) programming) tohave a fast expansion time once it achieves body temperature (which mayexceed the wet Tg for the foam). The foam may be stored in its moistureplasticized state.

Surgical implantation (as opposed to transcatheter implantation) mayhave body temperature actuation or higher for the foam.

In some embodiments (e.g., transcatheter or surgical) warm saline isused to expand the foam when ready.

When using foam instead of the conventional Dacron skirt, an embodimentcontains the foam in a lubricious sheath (e.g., a sheath made from PTFE)and the surgeon retracts the sheath when she or he is ready to deploythis device. This will minimize the amount of shear force on the foamconsidering, for example, PTFE is more slippery/has less resistance thatmost PU catheters.

Embodiments may include low and/or high density foams. In embodimentsdensity is used to balance the mechanical strength of the foam (e.g.,higher density reduces shearing/tearing) while minimizing the crimpdiameter (e.g., higher density decreases the ability to crimp the foam).An embodiment includes a foam with pore sizes between 50-1500 microns.

Some embodiments ensure the foam does not deploy into the main vessel.For example, the foam is well adhered to support structure and expandsradially outward from the lumen. Foam pieces adhered to the valve shouldnot compromise the heart chambers. For example, in an embodimentmechanical constraint is used to prevent the foam from deployingradially inward into the main vessel. For instance, the valve mayprevent the inward expansion of the foam. As another example, a polymermembrane located between the foam and the device inner channel mayprevent the inward expansion of the foam.

Embodiments may include scales that are not all identical. For example,an embodiment includes multiple rows of scales, some of which includehalf scales and others of which include full scales. The rows mayalternate between two different patterns of scales and/or size ofscales.

An embodiment uses both a Dacron skirt and SMP foam. For example, theDacron skirt acts like a “sheath” of sorts that folds over the crimpedfoam to help delivery.

Embodiments may be used in different pressure environments (e.g., venousvs. arterial pressure). Such embodiments may employ different poresize/form factors from each other.

Embodiments may also address perivalvular leak for venous valvereplacement devices, such as in large veins of the leg.

FIG. 1 includes a system 100 with a stent that includes first, second,third, and fourth struts 101, 102, 103, 104. The stent further includesfirst, second, third, fourth, and fifth windows 111, 112, 113, 114, 115.Valve 121 is included within the stent (best visible in FIG. 2B). Anopen-cell polyurethane thermoset SMP foam 131 is configured to expandfrom a compressed secondary state to an expanded primary state inresponse to thermal stimulus; and an outer conduit that includes thestent. In FIG. 1 the first and third windows 111, 113 share the firststrut 101 and are both immediately adjacent the first strut. The secondand third windows 112, 113 share the second strut 102 and are bothimmediately adjacent the second strut. The fourth and third windows 113,113 share the third strut 103 and are both immediately adjacent thethird strut. The fifth and third windows 115, 113 share the fourth strut104 and are both immediately adjacent the fourth strut. While struts101, 103 may be included in a single monolithic length of wire, theyconstitute separate “struts” as that term is used herein.

In FIG. 1, the SMP foam 131 substantially covers at least 80% of a firstface of the third window. This “face” is likely 95% obscured (or more)in the embodiment of FIG. 1. The face is primarily formed by struts 101,102, 103, 104.

In an embodiment, the first, second, third, and fourth struts eachinclude a shape memory metal, such as Nitinol. However, otherembodiments are not so limited and my include stainless steel or othermetals. Such non-shape memory metals may be deployed with aid of aballoon or other expansive device. Other embodiments include valves thatare surgically implanted.

In FIG. 1, the first and second struts 101, 102 fixedly couple to theSMP foam, and the third and fourth struts 103, 104 do not fixedly coupleto the SMP foam. The relevance of this arrangement is expanded uponbelow. Thus, while foam 131 may touch strut 103 is it not “fixed” tostrut 103 and when strut 103 deflects due to lengthening of the stent,foam 131 does not necessarily move with the strut. However, foam 131 isfixed to strut 101 and consequently moves when strut 101 moves. In otherwords, movement of foam 131 is dependent on strut 101 but not strut 103.

In a first orientation (e.g., when the system is in packaging beingshipped to a medical facility), the stent has a first maximum stentouter diameter. As shown in FIG. 3B, window 313 (analogous to window 113of FIG. 1) has a first window length 340′ measured parallel to a longaxis 341 of the stent. Also, the window has a first window width 342′measured orthogonal to the long axis of the stent and parallel to ashort axis 343 of the stent. The SMP foam 331 is in the compressedsecondary state.

In a second orientation the stent has a second maximum stent outerdiameter 342 that is greater than the first maximum stent outer diameter342′. This occurs because to reduce the footprint of the stent (to readystent for implantation) the stent is compressed (and possibly folded).When doing so the stent may be lengthened along axis 341, which causesnecking (narrowed) along axis 343. As a result, window 313 has a secondwindow length 340 that is less than the first window length 340′. Also,window 313 has a second window width 342 that is greater than the firstwindow width 342′. The SMP foam is in the expanded primary state in thesecond orientation.

In contrast to the changing length of window 313, SMP foam 331 has thesame foam length (at least in some embodiments) in the compressed andexpanded states. For example, length 344′ is substantially (+/−3%) thesame as length 344. In some embodiments the foam may have the same widthin the compressed and expanded states (although the width appears tochange in FIGS. 3A and 3B, in some embodiments the width of the foamdoes not change). The consistent foam length and width is consideredbefore any folding or pleating of the system occurs. In embodiments theonly compression of foam 331 is radial compression (into the page ofFIG. 3A), with little or no axial (along axis 341) or circumferential(generally along axis 343) compression/expansion.

Applicant recognized these “crimping dynamics” exist and concern theissue that the metal stent may deform (i.e., axially) to a greaterdegree than the SMP foam. Further, Applicant recognized that metals suchas Nitinol may have a relatively low strain capacity (e.g., 4%) whereasthe SMP foam has a relatively high strain capacity. Thus, when the metalstent deforms a great deal axially (along axis 341) that deformation maybe greater than any axial deformation of the SMP foam. For example,there may little to no axial deformation of the SMP foam. Thus, aradially compressed SMP foam may not be able to deform to the extent ofmetal window length differential 340″ (340′−340=340″). In variousembodiments any axial lengthening of the foam may be 0, 5, 10, 15, or20% of the axial differential 340″.

In response to these crimping dynamics, an embodiment secures foam 331to some struts of the stent but not to others. For example, in FIG. 1SMP foam 131 fixedly couples to struts 101, 102 at locations 151, 151′and 152, 152′. Locations 151, 151′ and 152, 152′ are where struts 101,102 repeatedly pierce SMT foam 131, thereby securing foam 131 to thestent. In other words, strut 101 pierces the SMP foam 131 in at leastone location (e.g., location 151) such that the first strut traversesfrom a first face of the SMP foam (front face seen in FIG. 1) to asecond face of the SMP foam (back face not seen in FIG. 1), the firstand second faces opposing each other. Notice the lower half of SMT foam131 is not fixedly secured to struts 103, 104. In response to the firstand second struts 101, 102 fixedly coupling to the SMP foam 131, and thethird and fourth struts 103, 104 not fixedly coupling to the SMP foam,the SMP foam is configured to move dependent upon the first and secondstruts and independent of the third and fourth struts when the apparatustransitions from the first orientation to the second orientation. Forexample, in FIGS. 3A and 3B foam 331 should “ride” up and down (or slideup and down along axis 341) when struts 301, 302 move up and down alongaxis 341. However, an extreme deflection downwards by struts 303, 304should not rip or damage the cells of SMT foam 331 since the foam islargely independent of movements of struts 303, 304.

Regarding the coupling of foam 131 to various struts, the SMT foam maycouple to the stent in other ways. For example, in an embodiment anadhesive (e.g., UV epoxy weld that uses Dymax 203A-CTH-F to bind Nitinolstrut to polyurethane of the SMP foam) couples the SMP foam 131 to thefirst and second struts 101, 102. The adhesive may be applied alonglength 161, 162 but absent from length 161′, 162′ and further absentfrom struts 103, 104. The adhesive is not seen in FIG. 1 as it isbetween foam 131 and the struts. Masking may be used at areas 161′,162′, 103, 104 to ensure no adhesive is applied to those areas. Themasking (e.g., an oxide or nitride) may then be removed later in theprocess in some embodiments.

In an embodiment the adhesive includes an un-foamed polyurethane coatingdirectly contacting the first strut 101 and fixedly attached to thefirst strut. The SMP foam 131 directly contacts the polyurethane coatingand fixedly attaches to the polyurethane coating. As a result, thepolyurethane coating fixedly attaches the SMP foam 131 to the firststrut 101. Thus, for a polyurethane foam the adhesion to anotherpolyurethane provides for a stronger adhesion between the adhesive andthe foam. For example, the un-foamed polyurethane coating may include aneat polyurethane.

In an embodiment the polyurethane coating is a cured thermoset. However,in another embodiment the polyurethane coating is a thermoplastic. In anembodiment the polyurethane coating has a chemical composition equal toa chemical composition of the SMP foam. Thus, the adhesion between thefoam and adhesive is “like to like” and consequently reliable. Forexample, both the SMP foam and the adhesive coating may be derived froma reaction between one or more polyols (e.g., HPED and/or TEA) and oneor more diisocyanates (e.g., hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), and/or isophorone diisocyanate).

In an embodiment, the polyurethane coating is a SMP. That SMP coatingmay have the same chemical composition of the SMP foam. In an embodimentSMP coating is foamed thereby providing a first foam (inner foam) thatcouples a second foam (outer foam 131) to the stent strut.

Further regarding the makeup of foam 131, in an embodiment the SMP foamis covalently bonded to iodine to thereby make the foam visible underX-ray imaging (i.e., radiopaque). Again regarding radio-opacity, in anembodiment the SMP foam is a poly(urethane-urea-amide). In an embodimentthe iodine is included in a triiodobenzene monomer.

As mentioned above, in the compressed state the foam 131 is compressedradially along a radius 155 that is orthogonal to both the long axis 141of the stent and the short axis 143 of the stent. This is better seen inFIG. 2A (compressed) and 2B (expanded radially).

Various embodiments use one or more foam segments in various ways.

For example, in FIG. 1 the SMP foam 131 substantially covers a majorityof the face of window 113 but does not cover a majority of any face ofany of the first, second, fourth, and fifth windows 111, 112, 114, 115.In the embodiment of FIG. 1, window 113 is immediately adjacent each ofthe first, second, fourth, and fifth windows 111, 112, 114, 115. Noadditional stent window is between the window 114 and any of the windows111, 112, 114, 115.

For example, FIG. 2A discloses SMP foam 131. Further, FIG. 2A includesan additional open-cell polyurethane thermoset SMP foam 132, theadditional SMP foam being configured to expand from a compressedsecondary state to an expanded primary state in response to thermalstimulus. Foam 132 substantially covers a first face of the fourthwindow 215, the fourth window having the first face and a second facethat oppose one another. At least a portion of fourth strut 104 fixedlycouples to the additional SMP foam 132 (but not to foam 131). In thefirst orientation the additional SMP foam is in the compressed secondarystate and in a second orientation the additional SMP foam is in theexpanded primary state.

In an embodiment, foam 131 may be slightly enlarged such that foam 131extends to boundaries 131′. As a result the enlarged SMP foam 131 andthe additional SMP foam 132 overlap one another (see area 133 for areaof overlap) such that an axis (see dot 155′ showing axis going into thepage) intersects both the SMP foam 131 and the additional SMP foam 132.Axis 155′ is orthogonal to the long axis 141 of the stent and to theshort axis 143 of the stent.

As seen in FIG. 2A, SMP foam 131 has a first surface area. Additionalfoam 132 has a second surface area. The first surface area is at least20% greater than the second surface area. However, in other embodimentsone foam segment may be 30, 40, 50, 60, 70, 80, 90% or more greater insurface area than another foam segment.

In the Embodiment of FIG. 2B, foam 131 exists in conjunction with foam135. Additional open-cell polyurethane thermoset SMP foam 135 isconfigured to expand from a compressed secondary state to an expandedprimary state in response to thermal stimulus. Additional SMP foam 135substantially covers a first face of a sixth window 216 included in thestent; the sixth window having the first face and a second face thatoppose one another. Additional SMP foam 135 does not substantially coverthe third window 113. SMP foam 131 does not substantially cover thesixth window 216. An additional strut 201 fixedly couples to theadditional SMP foam 135 (similar to how strut 101 couples to foam 131),the additional strut being included in the sixth window 216. In thefirst orientation the additional SMP foam 135 is in the compressedsecondary state and in a second orientation the additional SMP foam isin the expanded primary state.

Again regarding FIG. 1, a first plane 157, parallel to the short axis143 of the stent, intersects the SMP foam 131, the first and secondstruts 101, 102, and the first, second, and third windows 111, 112, 113.A second plane 158, parallel to the short axis of the stent, intersectsthe SMP foam 131, the third and fourth struts 103, 104, and the third,fourth, and fifth windows 113, 114, 115. The first plane 157 does notintersect either of the third and fourth struts 103, 104. The firstplane 157 does not intersect either of the fourth and fifth windows 114,115. The second plane 158 does not intersect either of the first andsecond struts 101, 102. The second plane 158 does not intersect eitherof the first and second windows 111, 112.

In the embodiment of FIG. 1, the first strut 101 couples to the secondstrut 102 at a first junction 108. An axis 109 (see dot going into thepage) intersects the first junction but does not interface the SMP foam131. The axis 109 is orthogonal to the long axis 141 of the stent andthe short axis 143 of the stent. As mentioned above, a strut 101 may be“threaded” through the foam 131 before struts 101, 102 are coupled(e.g., weld) to one another. Therefore a window or void having sidewalls107, 107′ may be formed so the coupling (e.g., weld) can be formedwithout interference from the already present foam 131.

Regarding the “outer conduit” mentioned above, an embodiment may use aconduit (e.g., tube, sheath, skirt, catheter) to deploy the foam/stentsystem. In an embodiment the outer conduit includespolytetrafluoroethylene (PTFE), extruded PTFE (ePTFE), or some otherrelatively low friction material that will put limited shear force onthe SMP foam.

Some embodiments may include other conduits in addition or in lieu ofthe above “outer conduit.” For example, an embodiment may include aninner conduit (such as a polyurethane membrane) between the valve andthe SMP foam. For instance, a Dacron skirt (or any of various polymerskirts/conduits in various embodiments such as a polyurethane skirt) maybe between the valve and stent and may serve to ensure the SMP foam doesnot expand into main vessel (e.g., aorta). In other embodiments theinner conduit may be between the stent and the SMP foam. An adhesive maycouple the foam to the inner conduit. The inner conduit may be coupledto the struts. In such a manner the foam is coupled to the struts viathe adhesive and the inner conduit. In one embodiment, a non-foamed SMPadhesive adheres an SMP foam (having the same chemical composition asthe adhesive) to a non-shape memory inner conduit (e.g., polyurethaneinner conduit), which is coupled to the stent.

As seen in FIG. 4, an embodiment includes a SMP foam that comprises amonolithic SMP foam ring. The SMP foam ring may be outside the stent andsurround the stent. The ring may include creases or pleats to helpfacilitate controlled, repeatable collapsing of the ring when the stentis folded to minimize its profile for implantation. A portion of anupper half of the ring may be fixed to struts while a lower half of thering may not be fixed to the struts such that the bottom half is notstretched too far when stent is stretched axially.

The following examples pertain to further embodiments.

Example 1: An apparatus comprising: a stent that includes (a)(i) first,second, third, and fourth struts, and (a)(ii) first, second, third,fourth, and fifth windows; a valve included within the stent; anopen-cell polyurethane thermoset shape memory polymer (SMP) foam, theSMP foam being configured to expand from a compressed secondary state toan expanded primary state in response to thermal stimulus; and an outerconduit that includes the stent; wherein (b)(i) the first and thirdwindows share the first strut and are both immediately adjacent thefirst strut, (b)(ii) the second and third windows share the second strutare both immediately adjacent the second strut, (b)(iii) the fourth andthird windows share the third strut are both immediately adjacent thethird strut, and (b)(iv) the fifth and third windows share the fourthstrut are both immediately adjacent the fourth strut; wherein the SMPfoam substantially covers at least 80% of a first face of the thirdwindow, the third window having the first face and a second face thatoppose one another; wherein (c)(i) the first and second struts fixedlycouple to the SMP foam, and (c)(ii) the third and fourth struts do notfixedly couple to the SMP foam; wherein in a first orientation (d)(i)the stent has a first maximum stent outer diameter, (d)(ii) the thirdwindow has a first window length measured parallel to a long axis of thestent, (d)(iii) the third window has a first window width measuredorthogonal to the long axis of the stent and parallel to a short axis ofthe stent, and (d)(iv) the SMP foam is in the compressed secondarystate; wherein in a second orientation (e)(i) the stent has a secondmaximum stent outer diameter that is greater than the first maximumstent outer diameter; (e)(ii) the third window has a second windowlength that is less than the first window length, (e)(iii) the thirdwindow has a second window width that is greater than the first windowwidth, and (e)(iv) the SMP foam is in the expanded primary state;wherein in response to the first and second struts fixedly coupling tothe SMP foam, and the third and fourth struts not fixedly coupling tothe SMP foam, the SMP foam is configured to move dependent upon thefirst and second struts and independent of the third and fourth strutswhen the apparatus transitions from the first orientation to the secondorientation.

In other embodiments the SMP foam substantially covers at least 50, 60,70, 90% of a first face of the third window.

In another version of Example 1: An apparatus comprising: a stent thatincludes (a)(i) first, second, third, and fourth struts, and (a)(ii)first, second, third, fourth, and fifth windows; a valve included withinthe stent; an open-cell polyurethane thermoset shape memory polymer(SMP) foam, the SMP foam being configured to expand from a compressedsecondary state to an expanded primary state in response to thermalstimulus; and an outer conduit that includes the stent; wherein (b)(i)the first and third windows share the first strut and are bothimmediately adjacent the first strut, (b)(ii) the second and thirdwindows share the second strut are both immediately adjacent the secondstrut, (b)(iii) the fourth and third windows share the third strut areboth immediately adjacent the third strut, and (b)(iv) the fifth andthird windows share the fourth strut are both immediately adjacent thefourth strut; wherein the SMP foam substantially covers at least 80% ofa first face of the third window, the third window having the first faceand a second face that oppose one another; wherein the first, second,third, and fourth struts each include a shape memory metal; wherein(c)(i) the first and second struts fixedly couple to the SMP foam, and(c)(ii) the third and fourth struts do not fixedly couple to the SMPfoam; wherein in a first orientation (d)(i) the stent has a firstmaximum stent outer diameter, (d)(ii) the third window has a firstwindow length measured parallel to a long axis of the stent, (d)(iii)the third window has a first window width measured orthogonal to thelong axis of the stent and parallel to a short axis of the stent, and(d)(iv) the SMP foam is in the compressed secondary state; wherein in asecond orientation (e)(i) the stent has a second maximum stent outerdiameter that is greater than the first maximum stent outer diameter;(e)(ii) the third window has a second window length that is less thanthe first window length, (e)(iii) the third window has a second windowwidth that is greater than the first window width, and (e)(iv) the SMPfoam is in the expanded primary state; wherein in response to the firstand second struts fixedly coupling to the SMP foam, and the third andfourth struts not fixedly coupling to the SMP foam, the SMP foam isconfigured to move dependent upon the first and second struts andindependent of the third and fourth struts when the apparatustransitions from the first orientation to the second orientation.

In another version of Example 1: An apparatus comprising: a stent thatincludes (a)(i) first, second, third, and fourth struts, and (a)(ii)first, second, third, fourth, and fifth windows; a valve included withinthe stent; an open-cell polyurethane thermoset shape memory polymer(SMP) foam, the SMP foam having already expanded from a compressedsecondary state to an expanded primary state; and an outer conduit thatincludes the stent; wherein (b)(i) the first and third windows share thefirst strut and are both immediately adjacent the first strut, (b)(ii)the second and third windows share the second strut and are bothimmediately adjacent the second strut, (b)(iii) the fourth and thirdwindows share the third strut and are both immediately adjacent thethird strut, and (b)(iv) the fifth and third windows share the fourthstrut and are both immediately adjacent the fourth strut; wherein theSMP foam substantially covers at least 80% of a first face of the thirdwindow, the third window having the first face and a second face thatoppose one another; wherein (c)(i) the first and second struts fixedlycouple to the SMP foam, and (c)(ii) the third and fourth struts do notfixedly couple to the SMP foam; wherein in a first orientation (d)(i)the stent has a first maximum stent outer diameter, (d)(ii) the thirdwindow has a first window length measured parallel to a long axis of thestent, (d)(iii) the third window has a first window width measuredorthogonal to the long axis of the stent and parallel to a short axis ofthe stent; wherein in a second orientation (e)(i) the stent has a secondmaximum stent outer diameter that is greater than the first maximumstent outer diameter; (e)(ii) the third window has a second windowlength that is less than the first window length, (e)(iii) the thirdwindow has a second window width that is greater than the first windowwidth.

Thus, in some embodiments a product may be shipped with the SMP foamalready having been transitioned from its compressed state to anon-compressed state (e.g., already having been plasticized).

Several embodiments discussed herein address windows and struts butembodiments are not limited to any one form of support structure. Metalor polymer support skeletons are viable options that benefit from SMPfoams to lessen or prevent a PVL. Further, the SMP foam may have aportion of an upper half of the foam coupled to the support structurewhile no portion of a bottom half of the SMP foam is coupled to thesupport structure. This allows for (as an example) lengthening of thesupport structure without harming a radially compressed SMP foam.

While examples have addressed transitioning a SMP foam to its primarystate in response to thermal stimulus, SMP foams may be stimulated basedon body temperature, warm saline solution, electromagnetic stimulationvia a field supplied external or internal to the body, light from afiber optic cable, interaction with current supplied via a wire that isin proximity to the foam, and the like.

In some embodiments, a hydrogel may be substituted for the SMP foam.

Example 2: The apparatus of example 1 wherein in the compressed statethe first foam is compressed radially along a radius that is orthogonalto both the long axis of the stent and the short axis of the stent.

Example 3: The apparatus of example 2 wherein: the SMP foam has a firstfoam length in the compressed state, the first foam length beingmeasured parallel to the long axis of the stent; the SMP foam has asecond foam length in the expanded state; the first foam length issubstantially equal to the second foam length.

Example 4: The apparatus of example 2 wherein the first strut piercesthe SMP foam in at least one location such that the first struttraverses from a first face of the SMP foam to a second face of the SMPfoam, the first and second faces opposing each other.

Example 5: The apparatus of example 2 wherein: the first strut couplesto the second strut at a first junction; an axis intersects the firstjunction but does not interface the SMP foam; the axis is orthogonal tothe long axis of the stent; the axis is orthogonal to the short axis ofthe stent.

Example 6: The apparatus of example 2 comprising an adhesive thatcouples the SMP foam to the first and second struts.

Example 7: The apparatus of example 6 wherein: the adhesive includes anun-foamed polyurethane coating directly contacting the first strut andfixedly attached to the first strut; the SMP foam directly contacts thepolyurethane coating and fixedly attaches to the polyurethane coating;wherein the polyurethane coating fixedly attaches the SMP foam to thefirst strut.

Example 8: The apparatus of example 7, wherein the polyurethane coatingis a cured thermoset.

Example 9: The apparatus of example 7, wherein the polyurethane coatingis a thermoplastic.

Example 10: The apparatus of example 7, wherein the polyurethane coatinghas a chemical composition equal to a chemical composition of the SMPfoam.

Example 11: The apparatus of example 10 wherein the polyurethane coatingis a SMP.

Example 12: The apparatus of example 6 comprising an inner conduitbetween the valve and the SMP foam.

For example, the inner conduit may include a thermoplastic polyurethanemembrane deposited over the stent struts. The SMP foam may then beadhered to the membrane with an adhesive. As described herein, theadhesive may include a polyurethane. Thus, an embodiment includes apolyurethane adhesive that adheres a polyurethane SMP foam to apolyurethane membrane (where the membrane adheres to the stent).

Example 13: The apparatus of example 2 wherein the outer conduitincludes polytetrafluoroethylene (PTFE).

Example 14: The apparatus of example 2 wherein the SMP foam iscovalently bonded to iodine.

Example 15: The apparatus of example 14 wherein the SMP foam is apoly(urethane-urea-amide).

Example 16: The apparatus of example 14 wherein the iodine is includedin a triiodobenzene monomer.

Example 17: The apparatus of example 2 wherein the SMP foam is derivedfrom a reaction between one or more polyols and one or morediisocyanates.

Example 18: The apparatus of example 2 wherein: the SMP foamsubstantially covers a majority of the first face of the third windowbut does not cover a majority of any face of any of the first, second,fourth, and fifth windows; the third window is immediately adjacent eachof the first, second, fourth, and fifth windows; no additional stentwindow is between the third window and any of the first, second, fourth,and fifth windows.

Example 19: The apparatus of example 2 wherein: an additional open-cellpolyurethane thermoset SMP foam, the additional SMP foam beingconfigured to expand from a compressed secondary state to an expandedprimary state in response to thermal stimulus; and wherein theadditional SMP foam substantially covers a first face of the fourthwindow, the fourth window having the first face and a second face thatoppose one another; wherein the third strut fixedly couples to theadditional SMP foam; wherein in the first orientation the additional SMPfoam is in the compressed secondary state; wherein in a secondorientation the additional SMP foam is in the expanded primary state.

Example 20: The apparatus of example 19 wherein: the SMP foam and theadditional SMP foam overlap one another such that an axis intersectsboth the SMP foam and the additional SMP foam; the axis is orthogonal tothe long axis of the stent; the axis is orthogonal to the short axis ofthe stent.

Example 21: The apparatus of example 2 wherein: an additional open-cellpolyurethane thermoset SMP foam, the additional SMP foam beingconfigured to expand from a compressed secondary state to an expandedprimary state in response to thermal stimulus; and wherein theadditional SMP foam substantially covers a first face of a sixth windowincluded in the stent; the sixth window having the first face and asecond face that oppose one another; wherein the additional SMP foamdoes not substantially cover the third window; wherein the SMP foam doesnot substantially cover the sixth window; wherein an additional strutfixedly couples to the additional SMP foam, the additional strut beingincluded in the sixth window; wherein in the first orientation theadditional SMP foam is in the compressed secondary state; wherein in asecond orientation the additional SMP foam is in the expanded primarystate.

Example 22: The apparatus of example 21 wherein: the SMP foam has afirst surface area; the additional foam has a second surface area; thefirst surface area is at least 20% greater than the second surface area.

While Example 22 addresses an embodiment with differently sized scalesor SMP foam segments, other embodiments may include SMP foam segments ofdiffering density, compression, porosity, and the like. For example, adenser foam may be included directly adjacent a valve annulus whilesandwiched axially by less dense foams. This may allow for the greaterdensity foam to withstand elevated forces not present in areas removedfrom the valve annulus.

Example 23: The apparatus of example 2, wherein: the SMP foam comprisesa monolithic SMP foam ring; the SMP foam ring is outside the stent andsurrounds the stent.

Example 24: The apparatus of example 2, wherein: a first plane, parallelto the short axis of the stent, intersects the SMP foam, the first andsecond struts, and the first, second, and third windows; a second plane,parallel to the short axis of the stent, intersects the SMP foam, thethird and fourth struts, and the third, fourth, and fifth windows; thefirst plane does not intersect either of the third and fourth struts;the first plane does not intersect either of the fourth and fifthwindows; the second plane does not intersect either of the first andsecond struts; the second plane does not intersect either of the firstand second windows.

Example 25. The apparatus of example 2, wherein the first, second,third, and fourth struts each include at least one of Nitinol, cobaltchromium, and stainless steel.

Example 26: An apparatus comprising: a metal skeleton that includesfirst, second, third, and fourth struts; a valve included within theskeleton; an open-cell polyurethane thermoset shape memory polymer (SMP)foam, the SMP foam being configured to expand from a compressedsecondary state to an expanded primary state in response to thermalstimulus; and wherein (a)(i) the first and second struts fixedly coupleto the SMP foam, and (a)(ii) the third and fourth struts do not fixedlycouple to the SMP foam; wherein in a first orientation (b)(i) the stenthas a first maximum stent outer diameter, (b)(ii) the stent has a firststent length measured parallel to a long axis of the stent, (b)(iii),and the SMP foam is in the compressed secondary state; wherein in asecond orientation (c)(i) the stent has a second maximum stent outerdiameter that is greater than the first maximum stent outer diameter;(e)(ii) the stent has a second stent length that is less than the firststent length, and (c)(iii) the SMP foam is in the expanded primarystate; wherein in response to the first and second struts fixedlycoupling to the SMP foam, and the third and fourth struts not fixedlycoupling to the SMP foam, the SMP foam is configured to move dependentupon the first and second struts and independent of the third and fourthstruts when the apparatus transitions from the first orientation to thesecond orientation; wherein a first plane, orthogonal to the long axisof the stent, intersects the SMP foam and the first and second struts;wherein a second plane, orthogonal to the long axis of the stent,intersects the SMP foam and the third and fourth struts; wherein thefirst plane does not intersect either of the third and fourth struts;wherein the second plane does not intersect either of the first andsecond struts.

Example 1a: An apparatus comprising: a structural support skeleton thatincludes first, second, third, and fourth struts; a valve includedwithin the skeleton; an open-cell polyurethane thermoset shape memorypolymer (SMP) foam, the SMP foam being configured to expand from acompressed secondary state to an expanded primary state in response tothermal stimulus; wherein (a)(i) the first and second struts fixedlycouple to the SMP foam, and (a)(ii) the third and fourth struts do notfixedly couple to the SMP foam; wherein in a first orientation (b)(i)the stent has a first maximum stent outer diameter, (b)(ii) the stenthas a first stent length measured parallel to a long axis of the stent,(b)(iii), and the SMP foam is in the compressed secondary state; whereinin a second orientation (c)(i) the stent has a second maximum stentouter diameter that is greater than the first maximum stent outerdiameter; (e)(ii) the stent has a second stent length that is less thanthe first stent length, and (c)(iii) the SMP foam is in the expandedprimary state; wherein in response to the first and second strutsfixedly coupling to the SMP foam, and the third and fourth struts notfixedly coupling to the SMP foam, the SMP foam is configured to movedependent upon the first and second struts and independent of the thirdand fourth struts when the apparatus transitions from the firstorientation to the second orientation; wherein a first plane, orthogonalto the long axis of the stent, intersects the SMP foam and the first andsecond struts; wherein a second plane, orthogonal to the long axis ofthe stent, intersects the SMP foam and the third and fourth struts;wherein the first plane does not intersect either of the third andfourth struts; wherein the second plane does not intersect either of thefirst and second struts.

Example 2a. The apparatus of example 1a wherein: an adhesive directlycontacts the first and second struts and SMP foam to directly adhere theSMP foam to each of the first and second struts; neither of the thirdand fourth struts directly contacts an adhesive that also directlycontacts the SMP foam.

Example 3a. The apparatus of example la comprising a membrane thatcontacts the first and second struts, wherein: a location within anupper half of the SMP foam directly adheres to the membrane via anadhesive that directly contacts both the membrane and the SMP foam; alower half of the SMP foam does not directly adhere to the membrane viaany adhesive and is configured to slide over the membrane as theapparatus transitions from the first orientation to the secondorientation.

Example 4a: The apparatus according to any one of examples 1a-3a whereinin the compressed state the first foam is compressed radially along aradius that is orthogonal to both the long axis of the stent and theshort axis of the stent.

Example 5a: The apparatus of example 4a wherein: the SMP foam has afirst foam length in the compressed state, the first foam length beingmeasured parallel to the long axis of the stent; the SMP foam has asecond foam length in the expanded state; the first foam length issubstantially equal to the second foam length.

Example 6a: The apparatus of example 4a wherein the first strut piercesthe SMP foam in at least one location such that the first struttraverses from a first face of the SMP foam to a second face of the SMPfoam, the first and second faces opposing each other.

Example 7a: The apparatus of example 4a wherein: the first strut couplesto the second strut at a first junction; an axis intersects the firstjunction but does not interface the SMP foam; the axis is orthogonal tothe long axis of the stent; the axis is orthogonal to the short axis ofthe stent.

Example 8a: The apparatus of example la comprising an adhesive thatcouples the SMP foam to the first and second struts.

Example 9a: The apparatus according to any of examples 2a to 8a wherein:the adhesive includes an un-foamed polyurethane coating directlycontacting the first strut and fixedly attached to the first strut; theSMP foam directly contacts the polyurethane coating and fixedly attachesto the polyurethane coating; wherein the polyurethane coating fixedlyattaches the SMP foam to the first strut.

Example 10a: The apparatus of example 9a, wherein the polyurethanecoating is a cured thermoset.

Example 11a: The apparatus of example 9a, wherein the polyurethanecoating is a thermoplastic.

Example 12a: The apparatus of example 9a, wherein the polyurethanecoating has a chemical composition equal to a chemical composition ofthe SMP foam.

Example 13a: The apparatus of example 12a wherein the polyurethanecoating is a SMP.

Example 14a: The apparatus of example 4a comprising an inner conduitbetween the valve and the SMP foam.

For example, the inner conduit may include a thermoplastic polyurethanemembrane deposited over the stent struts. The SMP foam may then beadhered to the membrane with an adhesive. As described herein, theadhesive may include a polyurethane. Thus, an embodiment includes apolyurethane adhesive that adheres a polyurethane SMP foam to apolyurethane membrane (where the membrane adheres to the stent).

Example 15a: The apparatus of example 4a wherein the outer conduitincludes polytetrafluoroethylene (PTFE).

Example 16a: The apparatus of example 4a wherein the SMP foam iscovalently bonded to iodine.

Example 17a: The apparatus of example 16a wherein the SMP foam is apoly(urethane-urea-amide).

Example 18a: The apparatus of example 16a wherein the iodine is includedin a triiodobenzene monomer.

Example 19a: The apparatus of example 4a wherein the SMP foam is derivedfrom a reaction between one or more polyols and one or morediisocyanates.

Example 20a: The apparatus of example 4a wherein: the SMP foamsubstantially covers a majority of the first face of the third windowbut does not cover a majority of any face of any of the first, second,fourth, and fifth windows; the third window is immediately adjacent eachof the first, second, fourth, and fifth windows; no additional stentwindow is between the third window and any of the first, second, fourth,and fifth windows.

Example 21a: The apparatus of example 4a wherein: an additionalopen-cell polyurethane thermoset SMP foam, the additional SMP foam beingconfigured to expand from a compressed secondary state to an expandedprimary state in response to thermal stimulus; and wherein theadditional SMP foam substantially covers a first face of the fourthwindow, the fourth window having the first face and a second face thatoppose one another; wherein the third strut fixedly couples to theadditional SMP foam; wherein in the first orientation the additional SMPfoam is in the compressed secondary state; wherein in a secondorientation the additional SMP foam is in the expanded primary state.

Example 22a: The apparatus of example 21a wherein: the SMP foam and theadditional SMP foam overlap one another such that an axis intersectsboth the SMP foam and the additional SMP foam; the axis is orthogonal tothe long axis of the stent; the axis is orthogonal to the short axis ofthe stent.

Example 23a: The apparatus of example 4a wherein: an additionalopen-cell polyurethane thermoset SMP foam, the additional SMP foam beingconfigured to expand from a compressed secondary state to an expandedprimary state in response to thermal stimulus; and wherein theadditional SMP foam substantially covers a first face of a sixth windowincluded in the stent; the sixth window having the first face and asecond face that oppose one another; wherein the additional SMP foamdoes not substantially cover the third window; wherein the SMP foam doesnot substantially cover the sixth window; wherein an additional strutfixedly couples to the additional SMP foam, the additional strut beingincluded in the sixth window; wherein in the first orientation theadditional SMP foam is in the compressed secondary state; wherein in asecond orientation the additional SMP foam is in the expanded primarystate.

Example 24a: The apparatus of example 23a wherein: the SMP foam has afirst surface area; the additional foam has a second surface area; thefirst surface area is at least 20% greater than the second surface area.

Example 25a: The apparatus of example 4a, wherein: the SMP foamcomprises a monolithic SMP foam ring; the SMP foam ring is outside thestent and surrounds the stent.

Example 26a. The apparatus of example 4a, wherein the first, second,third, and fourth struts each include at least one of Nitinol, cobaltchromium, and stainless steel.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. This description and the claims following include terms, suchas left, right, top, bottom, over, under, upper, lower, first, second,etc. that are used for descriptive purposes only and are not to beconstrued as limiting. For example, terms designating relative verticalposition refer to a situation where a side of a substrate is the “top”surface of that substrate; the substrate may actually be in anyorientation so that a “top” side of a substrate may be lower than the“bottom” side in a standard terrestrial frame of reference and stillfall within the meaning of the term “top.” The term “on” as used herein(including in the claims) does not indicate that a first layer “on” asecond layer is directly on and in immediate contact with the secondlayer unless such is specifically stated; there may be a third layer orother structure between the first layer and the second layer on thefirst layer. The embodiments of a device or article described herein canbe manufactured, used, or shipped in a number of positions andorientations. Persons skilled in the relevant art can appreciate thatmany modifications and variations are possible in light of the aboveteaching. Persons skilled in the art will recognize various equivalentcombinations and substitutions for various components shown in theFigures. It is therefore intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

What is claimed is:
 1. An apparatus comprising: a stent that includes(a)(i) first, second, third, and fourth struts, and (a)(ii) first,second, third, fourth, and fifth windows; a valve included within thestent; an open-cell polyurethane thermoset shape memory polymer (SMP)foam, the SMP foam being configured to expand from a compressedsecondary state to an expanded primary state in response to thermalstimulus; and an outer conduit that includes the stent; wherein (b)(i)the first and third windows share the first strut and are bothimmediately adjacent the first strut, (b)(ii) the second and thirdwindows share the second strut and are both immediately adjacent thesecond strut, (b)(iii) the fourth and third windows share the thirdstrut and are both immediately adjacent the third strut, and (b)(iv) thefifth and third windows share the fourth strut and are both immediatelyadjacent the fourth strut; wherein the SMP foam substantially covers atleast 80% of a first face of the third window, the third window havingthe first face and a second face that oppose one another; wherein (c)(i)the first and second struts fixedly couple to the SMP foam, and (c)(ii)the third and fourth struts do not fixedly couple to the SMP foam;wherein in a first orientation (d)(i) the stent has a first maximumstent outer diameter, (d)(ii) the third window has a first window lengthmeasured parallel to a long axis of the stent, (d)(iii) the third windowhas a first window width measured orthogonal to the long axis of thestent and parallel to a short axis of the stent, and (d)(iv) the SMPfoam is in the compressed secondary state; wherein in a secondorientation (e)(i) the stent has a second maximum stent outer diameterthat is greater than the first maximum stent outer diameter; (e)(ii) thethird window has a second window length that is less than the firstwindow length, (e)(iii) the third window has a second window width thatis greater than the first window width, and (e)(iv) the SMP foam is inthe expanded primary state; wherein in response to the first and secondstruts fixedly coupling to the SMP foam, and the third and fourth strutsnot fixedly coupling to the SMP foam, the SMP foam is configured to movedependent upon the first and second struts and independent of the thirdand fourth struts when the apparatus transitions from the firstorientation to the second orientation.